1. Field of the Invention
The technology described herein relates to bicycle frames.
2. Description of the Related Art
Historically, bicycle frames have been made from hollow metal tubes. These tubes are joined at their ends to form a frame upon which the various other components can be mounted. The metal tubes have been joined to one another by means of heavy lugs, braces or sleeves and held in place by welding, soldering, brazing or the like.
Recent advances in material sciences have made it possible to construct frames using lightweight non-metallic composite materials, such as carbon fiber. Carbon fiber materials provide the necessary strength and shock absorption for high performance cycling. The use of carbon fiber materials in bicycle frames has made it possible to reduce the weight of bicycles, which also improves performance.
Despite the advantages of lightweight non-metallic composite materials, such as carbon fiber, some riders still prefer the metal frames because metal provides stiffness and good power transmission.
To balance the advantages of metal frames with the advantages of lightweight non-metallic composite materials, some bicycle frames have been made from metal and non-metallic composite materials. For example, some of the tubes, lugs, or braces of the bicycle frame will made of metal while other tubes, lugs, or braces of the bicycle frame will made of non-metallic composite materials.
One example of such a bicycle frame is the Tarmac E5 frame from Specialized Bicycle Components, Inc. of Morgan Hill, Calif. The frame of the Tarmac E5 includes a head tube, a down tube, a bottom bracket, a lower portion of the seat tube, and chain stays that form an aluminum alloy undercarriage. The top tube, seat stays, and upper portion of the seat tube form a monocoque carbon fiber structure. The connection points on the alloy undercarriage are co-molded with the monocoque carbon fiber structure. Thus, the bottom portion of the seat tube is made of aluminum alloy while the top portion of the seat tube is made of carbon fiber. Where the bottom portion of the seat tube joins the top portion, a carbon fiber laminate layer surrounds the outside of the seat tube (including surrounding a portion of the aluminum tube) and another carbon fiber layer lines the inside of the seat tube (including lining that same portion of the aluminum tube). Although this frame combines aluminum and carbon fiber, the frame is not stiff enough to provide optimal power efficiency and corner acceleration.
As the sport of bicycling increases in popularity, there is a demand for better performing bicycle frames.